Avalanche Forecast
Issued: Mar 8th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Cornices.
mconlan,
Avalanche Canada
Buried weak layers remain possible to be triggered, where they exist. Cornices and sun-exposed slopes will deteriorate during the heat of the day, potentially increasing the likelihood of avalanche activity.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
MONDAY NIGHT: Clear skies, 10 km/h northeast wind, alpine temperature -6.
TUESDAY: Clear skies, 20 km/h southwest wind, alpine temperature -6 C, freezing level rising to 1500 m.
WEDNESDAY: Morning clear skies and afternoon clouds, 20 km/h southwest wind, alpine temperature -6 C.
THURSDAY: Cloudy with snowfall, accumulation 5 cm, 20 km/h southwest wind, alpine temperature -6 C.
Avalanche Summary
No new avalanches were observed on Sunday or Monday. On Saturday, we received a few images of a rider that triggered a persistent slab avalanche near Crowsnest Pass. The avalanche appeared to be large (size 2 or greater) and at below treeline or treeline elevation in a forest burn. It is suspected that the avalanche released on one or potentially both of the weak layers described in the Snowpack Summary, as the maximum slab depth was around 90 cm.
Snowpack Summary
A dusting of snow overlies a melt-freeze crust in many areas, with the exception being on north aspects above around 1700 m. Wind slabs may still exist on northerly aspects at alpine and treeline elevations, whereas windward slopes have been scoured to rocks or a hard crust. On solar aspects and below the freezing level, the snow may moisten during the heat of the day.
Around 40 to 60 cm of snow sits above a persistent weak layer of sugary faceted grains that was buried in mid-February. There have been a handful of avalanches that released on this layer in the past few weeks. There is another persistent weak layer that was buried at the end of January, found around 50 to 80 cm deep. This layer consists of feathery surface hoar, facets, and/or a hard melt-freeze crust. Periodic avalanches continue to be triggered on these layers.Â
Weak faceted snow and a decomposing melt-freeze crust can be found near the base of the snowpack.Â
Terrain and Travel
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Problems
Persistent Slabs
Two persistent weak layers exist in the snowpack:
- The upper layer is buried 30 to 60 cm and primarily consists of faceted grains.
- The deeper layer is buried 60 to 100 cm and consists of surface hoar, facets, and/or a crust. The problem has been most prevalent around treeline elevations and in openings below treeline, but also reaches into the lower alpine.
These layers could be triggered by riders anywhere they still exist. A mild, sunny Tuesday may increase the likelihood of triggering these layers.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices will weaken with sunny skies and relatively mild air temperature. The snow on sun-exposed slopes may also moisten, so use caution during the heat of the day.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 9th, 2021 4:00PM
